Method of photoengraving



printing from Ithe nished Patented Apr. 2.2, 1941 OFFICE ME'rnon or rnoronnoaavmo Thorlo N. Hoglund, Des Moines, Iowa applicati@ :une iz, 1939, seran No. z'zssas 4 claims. (ci. sas-5.7)

-The .principal object of [my invention is to accomplish desired staging and drop-outs automatically in the process of photoengraving.

A further object of Ithis invention is to provide a method wherein the plate, prio' to the etching phase, is of a darker tonethereby making possible a deeper etching without loss of color values.

A still further object of my invention is to provide a method whereby the ordinarysquare highlight dot lbecomes an elongated rectangular calone. 4

A still further object oi' my invention is .to pro` vide a method wherein the highlight dots are etched faster ythan the highlight dots next in size,

the middle tones are etched faster than the next `darker .t-ones, .the darker tones are etched very slowly, and the next darker tones are substantially free of etching.

A still further object of my invention is to provide a method of photoengraving wherein-the greater contr-ast.

A' still further object of my invention is to provide an'easymethod of photoengraving that is The usual way of making an etching on a plate 5 of copper, zinc or like is to sensltize the .plate with a suitable solution, common inthe trade,

one and a round shadow dot becomes an elliptiplate is capable oi i of an autoafter which the sensitized face is subjected to light through a, photographic half-.tone negative. Ob-

, viously, the negative is an ordinary one contain-l Y ing/the picture-impression oi 'the subject" matter to be vplaced on the plate. Where the light passes throughjthe .transparent and translucent parts o i the negative, the sensitized coating on the plate will adhere to the plate. 'I'he balance fof thevsensi-tized coating canbe washed away.

thereby leaving Iparts of .the metal plate exposed for etching. Any suitableetching solution may ybe used and after the plate has been subjected to such solutionl the image of the subject matter on the plate will be in relief, and obviously, the high points of the relief will become the printing part ci the plate when put into printing usage. How-1 ever, it will be noted that by etching or continuing the etching, these printing surfaces or places f -and smaller. 'Io` prevent this in certain instances and to produce a iinished plate of the desired t printing contrasts, certain of these tones are painted in or staged to prevent graying out and lthen the plate is subjected again .to the solution. This may be repeated many times in order to Vgain the desired result.

My method. however, is to eliminate such problems in photoengraving and I obtain a `better impression on the sensitized coating of the plate and change the shape of the ordinary round shadow dot and ordinary square highlight dot. After the initial subjecting of the plate to light through a negative, I resensitize the plate andV `then subject it .to a second exposure of light through Ithe negative. The plate is then developed. This means two separate exposures before the plate isA etched. The second exposure will provide darker ltones and this means one can etch maximum depths without lo'ss oi color values. In making the second exposure, the negative is slightly shiftedfin position in order that it will not exactly register with the rst impression. By this action, the square highlight dot becomes an elongated rectangular one and the round dot becomes an oval one.

A Although the double exposure in itself has great advantages for deep etching in the usual manner, .the shifting of the negative in the second exposure and .the changing of the outline oi',

' the dots has great potentialities in Ithe use of dragons blood powder, etching ink, and the like. The use of dragon's blood powder, ink and like .to ret-ard the etching processes after the iirst etching bite, on certain dots or sections oi a plate, are well known.

The signicance of this phase, however,- is

` is due to the fact that the nest shadow dot is too fine to keep open in any part, and, therefore,

etching has ceased. The sensltized coating or enamel on the plate is the same thickness on all dots and the larger dots are, therefore, not effected by the thickness of the enamel. On the other hand, the small shadow dots are practically closed by the enamel. :The part therefore left exposed for etching is apercentage relative to the size of the shadow dot. The smaller the dot, the less area for attack of the etching solution. This is because the smaller the shadow dots, the more they close up by enameling and powdering. Therefore, the highlight dots are etched faster than the dots next in size and the middle tones are etching faster than the next darker tones. Also, the next darker tones are etching very little and the dark tones not at all.

It should also be noted that the shadow dots which are elliptical-will, by the use of powder banked along their small inner ends, be etched into a round dot, thereby making such shadow dots their original shapeand size as if only one exposure had been made, color due to a darker print. This means that great depth has now been reached in the etching process and a dot which received but a very slight etch will now be closed and the other dots will close up in proportion to their size.

This leaves only the middle tones etching slightly, leaving highlight dots receiving most of the etching. l

Obviously, other effects may be obtained by powdering the plate in three directions or powder from each` of the four directions. This procedure leaves a larger percentage oi etching in the highlights. The shadow dots remain the same as herebefore explained.

Fig. 1 of the drawing illustrates the step by step procedure of my method.

Certain changes may be made in my method of photoengraving without departing from the spirit and purpose of this invention, and it is my intention to cover in my claims any reasonable modification thereof.

li claim: l

l.. A method of photoengraving comprising, the preparingof the surface of a plate with a suitable sensitized covering, the placement of a screened half-tone negative forward of and on the sensitized face of said plate, the p ci .light rays through said negative, and on to the but without loss of escasas f sensitized face of said plate, the resensitizing of the face of said plate with a suitable sensitized covering, the replacement of the said negative' forward of and on the sensitized face of said plate with the negative slightly shifted from its original position on said plate, the passing of light rays through said negative and on to the sensitized face of said plate, the washing of said plate and the etching of said plate with a suitable etching solution.

2. A method of photoengraving comprising, the preparing of the surface of a plate with a suitable sensitized covering, the placement of a screened half-tone negative on the sensitized face of said plate, the passing of .light rays through said negative, and on to the sensitized face of said plate, the resensitizing of the face of said plate with a suitable sensitized covering,

" the replacement ofthe negative on the sensitized face of said plate, and slightly shifted in its position relative to its rst position on said plate, the passing of light rays through said negative and on to the sensitized face of said plate, the washing of said plate and the etching of said plate with a suitable etching solution.

3. A method of photoengraving comprising, the preparing of the surface of a plate with a suitable sensitized covering, the placement of a screened half-tone negative on the face of said plate, the passing of light rays through said negative, and on to the sensitized face of said plate, the resensitizing of the face of said plate with a suitable sensitized covering, the replacement of the negative on the sensitized face of said plate, and slightly shifted in its position relative to its rst position on said plate, the passing of light rays through said negative and on to the sensitized face of said plate, the washing of said plate and the etching of said plate with a suitable etching solution, the subjecting of the plate to an etching powder, and the :re-subjecting of said plate to a suitable etching solution.

4. A method of photoengraving comprising, the

r preparing of the surface of a plate with a suitable sensitized covering, the placement of a screened half-tone-negative onf the face of said plate, the passing of light rays through said negative, and on to the sensitized face of said plate, the resensitizing of the face of said plate with a suitable sensitized covering, the replacement of the negative on the sensitized face of said plate, and slightly shifted in its position relative to its first position on said plate, the passing of light rays through said negative and on to the sensitized face of said plate, the washing of said plate and the etching of said plate with a suitable etching solution, the banking of the resultant dots with an etching powder from two directions, and a re-etching of said plate with a suitable etching solution.

THO N. HOGLUND. 

